Non-wireframe edges showing in object mode
If, after you had just created the new edges, and while they were still selected, you accidentally pressed Shift D, you would have made a copy of those edges, which will show up when in object mode, similar to how they are in your picture.  Try going into Edit mode and select just those edges - go to Edge mode, then right-click on one of the edges with Alt held down, then G (grab) them - if they come away from the rest of the mesh, then they're loose, duplicated edges and you can delete them.